The Effect of Lymphangiogenesis in Transplant Arteriosclerosis.

BACKGROUND: Transplant arteriosclerosis is a major complication in long-term survivors of heart transplantation. Increased lymph flow from donor heart to host lymph nodes has been reported to play a role in transplant arteriosclerosis, but how lymphangiogenesis affects this process is unknown. METHODS: Vascular allografts were transplanted among various combinations of mice, including wild-type, Lyve1-CreERT2;R26-tdTomato, CAG-Cre-tdTomato, severe combined immune deficiency, Ccr2KO, Foxn1KO, and lghm/lghdKO mice. Whole-mount staining and 3-dimensional reconstruction identified lymphatic vessels within the grafted arteries. Lineage tracing strategies delineated the cellular origin of lymphatic endothelial cells. Adeno-associated viral vectors and a selective inhibitor were used to regulate lymphangiogenesis. RESULTS: Lymphangiogenesis within allograft vessels began at the anastomotic sites and extended from preexisting lymphatic vessels in the host. Tertiary lymphatic organs were identified in transplanted arteries at the anastomotic site and lymphatic vessels expressing CCL21 (chemokine [C-C motif] ligand 21) were associated with these immune structures. Fibroblasts in the vascular allografts released VEGF-C (vascular endothelial growth factor C), which stimulated lymphangiogenesis into the grafts. Inhibition of VEGF-C signaling inhibited lymphangiogenesis, neointima formation, and adventitial fibrosis of vascular allografts. These studies identified VEGF-C released from fibroblasts as a signal stimulating lymphangiogenesis extending from the host into the vascular allografts. CONCLUSIONS: Formation of lymphatic vessels plays a key role in the immune response to vascular transplantation. The inhibition of lymphangiogenesis may be a novel approach to prevent transplant arteriosclerosis.

Peptide Vaccine Against ADAMTS-7 Ameliorates Atherosclerosis and Postinjury Neointima Hyperplasia.

BACKGROUND: The metalloprotease ADAMTS-7 (a disintegrin and metalloproteinase with thrombospondin type 1 motif 7) is a novel locus associated with human coronary atherosclerosis. ADAMTS-7 deletion protects against atherosclerosis and vascular restenosis in rodents. METHODS: We designed 3 potential vaccines consisting of distinct B cell epitopic peptides derived from ADAMTS-7 and conjugated with the carrier protein KLH (keyhole limpet hemocyanin) as well as aluminum hydroxide as an adjuvant. Arterial ligation or wire injury was used to induce neointima in mice, whereas ApoE-/- and LDLR-/- (LDLR [low-density lipoprotein receptor]) mice fed a high-fat diet were applied to assess atherosclerosis. In addition, coronary stent implantation was performed on vaccine-immunized Bama miniature pigs, followed by optical coherence tomography to evaluate coronary intimal hyperplasia. RESULTS: A vaccine, ATS7vac, was screened out from 3 candidates to effectively inhibit intimal thickening in murine carotid artery ligation models after vaccination. As well, immunization with ATS7vac alleviated neointima formation in murine wire injury models and mitigated atherosclerotic lesions in both hyperlipidemic ApoE-/- and LDLR-/- mice without lowering lipid levels. Preclinically, ATS7vac markedly impeded intimal hyperplasia in swine stented coronary arteries, but without significant immune-related organ injuries. Mechanistically, ATS7vac vaccination produced specific antibodies against ADAMTS-7, which markedly repressed ADAMTS-7-mediated COMP (cartilage oligomeric matrix protein) and TSP-1 (thrombospondin-1) degradation and subsequently inhibited vascular smooth muscle cell migration but promoted re-endothelialization. CONCLUSIONS: ATS7vac is a novel atherosclerosis vaccine that also alleviates in-stent restenosis. The application of ATS7vac would be a complementary therapeutic avenue to the current lipid-lowering strategy for atherosclerotic disease.

Outer Membrane Vesicles Released from Garlic Exosome-like Nanoparticles (GaELNs) Train Gut Bacteria that Reverses Type 2 Diabetes via the Gut-Brain Axis.

Gut microbiota function has numerous effects on humans and the diet humans consume has emerged as a pivotal determinant of gut microbiota function. Here, a new concept that gut microbiota can be trained by diet-derived exosome-like nanoparticles (ELNs) to release healthy outer membrane vesicles (OMVs) is introduced. Specifically, OMVs released from garlic ELN (GaELNs) trained human gut Akkermansia muciniphila (A. muciniphila) can reverse high-fat diet-induced type 2 diabetes (T2DM) in mice. Oral administration of OMVs released from GaELNs trained A. muciniphila can traffick to the brain where they are taken up by microglial cells, resulting in inhibition of high-fat diet-induced brain inflammation. GaELNs treatment increases the levels of OMV Amuc-1100, P9, and phosphatidylcholines. Increasing the levels of Amuc-1100 and P9 leads to increasing the GLP-1 plasma level. Increasing the levels of phosphatidylcholines is required for inhibition of cGas and STING-mediated inflammation and GLP-1R crosstalk with the insulin pathway that leads to increasing expression of Insulin Receptor Substrate (IRS1 and IRS2) on OMV targeted cells. These findings reveal a molecular mechanism whereby OMVs from plant nanoparticle-trained gut bacteria regulate genes expressed in the brain, and have implications for the treatment of brain dysfunction caused by a metabolic syndrome.

Unspliced XBP1 Counteracts ß-Catenin to Inhibit Vascular Calcification.

BACKGROUND: Vascular calcification is a prevalent complication in chronic kidney disease and contributes to increased cardiovascular morbidity and mortality. XBP1 (X-box binding protein 1), existing as the XBP1u (unspliced XBP1) and XBP1s (spliced XBP1) forms, is a key component of the endoplasmic reticulum stress involved in vascular diseases. However, whether XBP1u participates in the development of vascular calcification remains unclear. METHODS: We aim to investigate the role of XBP1u in vascular calcification. XBP1u protein levels were reduced in high phosphate-induced calcified vascular smooth muscle cells, calcified aortas from mice with adenine diet-induced chronic renal failure, and calcified radial arteries from patients with chronic renal failure. RESULTS: Inhibition of XBP1u rather than XBP1s upregulated in the expression of the osteogenic markers Runx2 (runt-related transcription factor 2) and Msx2 (msh homeobox 2), and exacerbated high phosphate-induced vascular smooth muscle cell calcification, as verified by calcium deposition and Alizarin red S staining. In contrast, XBP1u overexpression in high phosphate-induced vascular smooth muscle cells significantly inhibited osteogenic differentiation and calcification. Consistently, smooth muscle cell-specific XBP1 deficiency in mice markedly aggravated the adenine diet- and 5/6 nephrectomy-induced vascular calcification compared with that in the control littermates. Further interactome analysis revealed that XBP1u is bound directly to ß-catenin, a key regulator of vascular calcification, via amino acid (aa) 205-230 in its C-terminal degradation domain. XBP1u interacted with ß-catenin to promote its ubiquitin-proteasomal degradation and thus inhibited ß-catenin/TCF (T-cell factor)-mediated Runx2 and Msx2 transcription. Knockdown of ß-catenin abolished the effect of XBP1u deficiency on vascular smooth muscle cell calcification, suggesting a ß-catenin-mediated mechanism. Moreover, the degradation of ß-catenin promoted by XBP1u was independent of GSK-3ß (glycogen synthase kinase 3ß)-involved destruction complex. CONCLUSIONS: Our study identified XBP1u as a novel endogenous inhibitor of vascular calcification by counteracting ß-catenin and promoting its ubiquitin-proteasomal degradation, which represents a new regulatory pathway of ß-catenin and a promising target for vascular calcification treatment.

PHB2 Maintains the Contractile Phenotype of VSMCs by Counteracting PKM2 Splicing.

BACKGROUND: Phenotypic transition of vascular smooth muscle cells (VSMCs) accounts for the pathogenesis of a variety of vascular diseases during the early stage. Recent studies indicate the metabolic reprogramming may be involved in VSMC phenotypic transition. However, the definite molecules that link energy metabolism to distinct VSMC phenotype remain elusive. METHODS: A carotid artery injury model was used to study postinjury neointima formation as well as VSMC phenotypic transition in vivo. RNA-seq analysis, cell migration assay, collagen gel contraction assay, wire myography assay, immunoblotting, protein interactome analysis, co-immunoprecipitation, and mammalian 2-hybrid assay were performed to clarify the phenotype and elucidate the molecular mechanisms. RESULTS: We collected cell energy-regulating genes by using Gene Ontology annotation and applied RNA-Seq analysis of transforming growth factor-ß or platelet-derived growth factor BB stimulated VSMCs. Six candidate genes were overlapped from energy metabolism-related genes and genes reciprocally upregulated by transforming growth factor-ß and downregulated by platelet-derived growth factor BB. Among them, prohibitin 2 has been reported to regulate mitochondrial oxidative phosphorylation. Indeed, prohibitin 2-deficient VSMCs lost the contractile phenotype as evidenced by reduced contractile proteins. Consistently, Phb2SMCKO mice were more susceptible to postinjury VSMC proliferation and neointima formation compared with Phb2flox/flox mice. Further protein interactome analysis, co-immunoprecipitation, and mammalian 2-hybrid assay revealed that prohibitin 2, through its C-terminus, directly interacts with hnRNPA1, a key modulator of pyruvate kinase M1/2 (PKM) mRNA splicing that promotes PKM2 expression and glycolysis. Prohibitin 2 deficiency facilitated PKM1/2 mRNA splicing and reversion from PKM1 to PKM2, and enhanced glycolysis in VSMCs. Blocking prohibitin 2-hnRNPA1 interaction resulted in increased PKM2 expression, enhanced glycolysis, repressed contractile marker genes expression in VSMCs, as well as aggravated postinjury neointima formation in vivo. CONCLUSIONS: Prohibitin 2 maintains VSMC contractile phenotype by interacting with hnRNPA1 to counteract hnRNPA1-mediated PKM alternative splicing and glucose metabolic reprogramming.

Meta-Analysis of Single-Cell RNA-Seq Data Reveals the Mechanism of Formation and Heterogeneity of Tertiary Lymphoid Organ in Vascular Disease.

BACKGROUND: Tertiary lymphoid organs (TLOs) are ectopic lymphoid organs developed in nonlymphoid tissues with chronic inflammation, but little is known about their existence in different types of vascular diseases and the mechanism that mediated their development. METHODS: To take advantage of single-cell RNA sequencing techniques, we integrated 28 single-cell RNA sequencing data sets containing 5 vascular disease models (atherosclerosis, abdominal aortic aneurysm, intimal hyperplasia, isograft, and allograft) to explore TLOs existence and environment supporting its growth systematically. We also searched Medline, Embase, PubMed, and Web of Science from inception to January 2022 for published histological images of vascular remodeling for histological evidence to support TLO genesis. RESULTS: Accumulation and infiltration of innate and adaptive immune cells have been observed in various remodeling vessels. Interestingly, the proportion of such immune cells incrementally increases from atherosclerosis to intimal hyperplasia, abdominal aortic aneurysm, isograft, and allograft. Importantly, we uncovered that TLO structure cells, such as follicular helper T cells and germinal center B cells, present in all remodeled vessels. Among myeloid cells and lymphocytes, inflammatory macrophages, and T helper 17 cells are the major lymphoid tissue inducer cells which were found to be positively associated with the numbers of TLO structural cells in remodeled vessels. Vascular stromal cells also actively participate in vascular TLO genesis by communicating with myeloid cells and lymphocytes via CCLs (C-C motif chemokine ligands), CXCL (C-X-C motif ligand), lymphotoxin, BMP (bone morphogenetic protein) chemotactic, FGF-2 (fibroblast growth factor-2), and IGF (insulin growth factor) proliferation mechanisms, particularly for lymphoid tissue inducer cell aggregation. Additionally, the interaction between stromal cells and immune cells modulates extracellular matrix remodeling. Among TLO structure cells, follicular helper T, and germinal center B cells have strong interactions via TCR (T-cell receptor), CD40 (cluster of differentiation 40), and CXCL signaling, to promote the development and maturation of the germinal center in TLO. Consistently, by reviewing the histological images from the literature, TLO genesis was found in those vascular remodeling models. CONCLUSIONS: Our analysis showed the existence of TLOs across 5 models of vascular diseases. The mechanisms that support TLOs formation in different models are heterogeneous. This study could be a valuable resource for understanding and discovering new therapeutic targets for various forms of vascular disease.

Stem cell antigen-1+cell-derived fibroblasts are crucial for cardiac fibrosis during heart failure.

AIMS: Mesenchymal stem cells (MSCs) present in the heart cannot differentiate into cardiomyocytes, but may play a role in pathological conditions. Therefore, the aim of this study was to scrutinise the role and mechanism of MSC differentiation in vivo during heart failure. METHODS AND RESULTS: We performed single-cell RNA sequencing of total non-cardiomyocytes from murine and adult human hearts. By analysing the transcriptomes of single cells, we illustrated the dynamics of the cell landscape during the progression of heart hypertrophy, including those of stem cell antigen-1 (Sca1)+ stem/progenitor cells and fibroblasts. By combining genetic lineage tracing and bone marrow transplantation models, we demonstrated that non-bone marrow-derived Sca1+ cells give rise to fibroblasts. Interestingly, partial depletion of Sca1+ cells alleviated the severity of myocardial fibrosis and led to a significant improvement in cardiac function in Sca1-CreERT2;Rosa26-eGFP-DTA mice. Similar non-cardiomyocyte cell composition and heterogeneity were observed in human patients with heart failure. Mechanistically, our study revealed that Sca1+ cells can transform into fibroblasts and affect the severity of fibrosis through the Wnt4-Pdgfra pathway. CONCLUSIONS: Our study describes the cellular landscape of hypertrophic hearts and reveals that fibroblasts derived from Sca1+ cells with a non-bone marrow source largely account for cardiac fibrosis. These findings provide novel insights into the pathogenesis of cardiac fibrosis and have potential therapeutic implications for heart failure. Non-bone marrow-derived Sca1+ cells differentiate into fibroblasts involved in cardiac fibrosis via Wnt4-PDGFRα pathway.

Tip60-FOXO regulates JNK signaling mediated apoptosis in Drosophila.

The JNK signaling pathway plays crucial roles in various physiological processes, including cell proliferation, differentiation, migration, apoptosis, and stress response. Dysregulation of this pathway is closely linked to the onset and progression of numerous major diseases, such as developmental defects and tumors. Identifying and characterizing novel components of the JNK signaling pathway to enhance and refine its network hold significant scientific and clinical importance for the prevention and treatment of associated cancers. This study utilized the model organism Drosophila and employed multidisciplinary approaches encompassing genetics, developmental biology, biochemistry, and molecular biology to investigate the interplay between Tip60 and the JNK signaling pathway, and elucidated its regulatory mechanisms. Our findings suggest that loss of Tip60 acetyltransferase activity results in JNK signaling pathway activation and subsequent induction of JNK-dependent apoptosis. Genetic epistasis analysis reveals that Tip60 acts downstream of JNK, paralleling with the transcription factor FOXO. The biochemical results confirm that Tip60 can bind to FOXO and acetylate it. Introduction of human Tip60 into Drosophila effectively mitigates apoptosis induced by JNK signaling activation, underscoring conserved regulatory role of Tip60 in the JNK signaling pathway from Drosophila to humans. This study further enhances our understanding of the regulatory network of the JNK signaling pathway. By revealing the role and mechanism of Tip60 in JNK-dependent apoptosis, it unveils new insights and potential therapeutic avenues for preventing and treating associated cancers.

ATP promotes resident CD34+ cell migration mainly through P2Y2-Stim1-ERK/p38 pathway.

Extracellular adenosine triphosphate (ATP) is one of the most abundant biochemical constitutes within the stem cell microenvironment and is postulated to play critical roles in cell migration. However, it is unclear whether ATP regulates the cell migration of CD34+ vascular wall-resident stem/progenitor cells (VW-SCs) and participates in angiogenesis. Therefore, the biological mechanisms of cell migration mediated by ATP was determined by in vivo subcutaneous matrigel plug assay, ex vivo aortic ring assay, in vitro transwell migration assay, and other molecular methods. In the present study, ATP dose-dependently promoted CD34+ VW-SCs migration, which was more obviously attenuated by inhibiting or knocking down P2Y2 than P2Y6. Furthermore, it was confirmed that ATP potently promoted the migration of resident CD34+ cells from cultured aortic artery rings and differentiation into endothelial cells in matrigel plugs by using inducible lineage tracing Cd34-CreERT2; R26-tdTomato mice, whereas P2Y2 and P2Y6 blocker greatly inhibited the effect of ATP. In addition, ATP enhanced the protein expression of stromal interaction molecule 1 (STIM1) on cell membrane, blocking the calcium release-activated calcium (CRAC) channel with shSTIM1 or BTP2 apparently inhibited ATP-evoked intracellular Ca2+ elevation and channel opening, thereby suppressing ATP-driven cell migration. Moreover, extracellular signal-regulated protein kinase (ERK) inhibitor PD98059 and p38 inhibitor SB203580 remarkably inhibited ERK and p38 phosphorylation, cytoskeleton rearrangement, and subsequent cell migration. Unexpectedly, it was found that knocking down STIM1 greatly inhibited ATP-triggered ERK/p38 activation. Taken together, it was suggested that P2Y2 signaled through the CRAC channel mediated Ca2+ influx and ERK/p38 pathway to reorganize the cytoskeleton and promoted the migration of CD34+ VW-SCs.NEW & NOTEWORTHY In this study, we observed that the purinergic receptor P2Y2 is critical in the regulation of vascular wall-resident CD34+ cells' migration. ATP could activate STIM1-mediated extracellular Ca2+ entry by triggering STIM1 translocation to the plasma membrane, and knockdown of STIM1 prevented ERK/p38 activation-mediated cytoskeleton rearrangement and cell migration.

Multilineage contribution of CD34+ cells in cardiac remodeling after ischemia/reperfusion injury.

The ambiguous results of multiple CD34+ cell-based therapeutic trials for patients with heart disease have halted the large-scale application of stem/progenitor cell treatment. This study aimed to delineate the biological functions of heterogenous CD34+ cell populations and investigate the net effect of CD34+ cell intervention on cardiac remodeling. We confirmed, by combining single-cell RNA sequencing on human and mouse ischemic hearts and an inducible Cd34 lineage-tracing mouse model, that Cd34+ cells mainly contributed to the commitment of mesenchymal cells, endothelial cells (ECs), and monocytes/macrophages during heart remodeling with distinct pathological functions. The Cd34+-lineage-activated mesenchymal cells were responsible for cardiac fibrosis, while CD34+Sca-1high was an active precursor and intercellular player that facilitated Cd34+-lineage angiogenic EC-induced postinjury vessel development. We found through bone marrow transplantation that bone marrow-derived CD34+ cells only accounted for inflammatory response. We confirmed using a Cd34-CreERT2; R26-DTA mouse model that the depletion of Cd34+ cells could alleviate the severity of ventricular fibrosis after ischemia/reperfusion (I/R) injury with improved cardiac function. This study provided a transcriptional and cellular landscape of CD34+ cells in normal and ischemic hearts and illustrated that the heterogeneous population of Cd34+ cell-derived cells served as crucial contributors to cardiac remodeling and function after the I/R injury, with their capacity to generate diverse cellular lineages.

Highly sensitive and selective detection of nitrite using a fiber optofluidic laser.

Nitrite ion (NO2-) is a common contaminant that can significantly threaten human health and the environment. In this study, we demonstrate a chemical sensing platform to monitor the nitrite concentration using a fiber optofluidic laser (FOFL). An optical fiber, integrated into a microchannel, is used both as an optical micro-cavity and the sensing element. Rhodamine 6 G (Rh6G) in an aqueous micellar solution is used as the laser gain medium. The light intensity change of the lasing spectra is employed as an indicator for the NO2- ion concentration sensing. The lasing properties under different NO2- ion concentrations are experimentally and theoretically investigated to examine the sensing performance of the FOFL. The results show that the limit detection of the FOFL sensor is 0.54 µM, which is 2-order-of-magnitude lower than fluorescence measurement. The sensing mechanism of Rh6G for NO2- detection is studied by using density functional theory (DFT). The calculation results indicate that nitrite influences the electronic distribution of Rh6G based on the heavy atom effect, which leads to the fluorescence quenching of Rh6G in the excited state. In addition, the detection system exhibits favorable selectivity for NO2- ions.

ATP purinergic receptor signalling promotes Sca-1+ cell proliferation and migration for vascular remodelling.

AIMS: Vascular resident stem cells expressing stem cell antigen-1 (Sca-1+ cells) promote vascular regeneration and remodelling following injury through migration, proliferation and differentiation. The aim of this study was to examine the contributions of ATP signalling through purinergic receptor type 2 (P2R) isoforms in promoting Sca-1+ cell migration and proliferation after vascular injury and to elucidate the main downstream signalling pathways. METHODS AND RESULTS: ATP-evoked changes in isolated Sca-1+ cell migration were examined by transwell assays, proliferation by viable cell counting assays and intracellular Ca2+ signalling by fluorometry, while receptor subtype contributions and downstream signals were examined by pharmacological or genetic inhibition, immunofluorescence, Western blotting and quantitative RT-PCR. These mechanisms were further examined in mice harbouring TdTomato-labelled Sca-1+ cells with and without Sca-1+-targeted P2R knockout following femoral artery guidewire injury. Stimulation with ATP promoted cultured Sca-1+ cell migration, induced intracellular free calcium elevations primarily via P2Y2R stimulation and accelerated proliferation mainly via P2Y6R stimulation. Enhanced migration was inhibited by the ERK blocker PD98059 or P2Y2R-shRNA, while enhanced proliferation was inhibited by the P38 inhibitor SB203580. Femoral artery guidewire injury of the neointima increased the number of TdTomato-labelled Sca-1+ cells, neointimal area and the ratio of neointimal area to media area at 3 weeks post-injury, and all of these responses were reduced by P2Y2R knockdown. CONCLUSIONS: ATP induces Sca-1+ cell migration through the P2Y2R-Ca2+-ERK signalling pathway, and enhances proliferation through the P2Y6R-P38-MAPK signalling pathway. Both pathways are essential for vascular remodelling following injury. Video Abstract.

Nonbone Marrow CD34+ Cells Are Crucial for Endothelial Repair of Injured Artery.

[Figure: see text].

Large dynamic range dual-mode pH sensors via dye-doped ionic liquid fiber optofluidic lasers.

We report a fiber optofluidic laser (FOFL) using an RhB-doped ionic liquid (BmimPF6) as the gain medium and explore its application for large dynamic range highly sensitive pH sensing. Due to the high Q-factor of the FOFL and the unique merits of BmimPF6, lasing emission presents a threshold of only 0.61 µJ mm-1. Particularly, lasing emission behaviors are strongly dependent on the pH value of the gain medium, i.e., in the pH range 4.28-6.37, the lasing central wavelength blue-shifts monotonically with a sensitivity as high as 5.02 nm per pH unit, which we attribute to the conversion of the cationic form of RhB to the zwitterionic form caused by the deprotonation of the COOH group. Under alkaline conditions (pH 7.20-11.17), the lasing emission intensity exhibits a significant decrease and the corresponding lasing central wavelength is also blue-shifted due to the solvent effect. The sensitivity based on the wavelength shift is 3.03 nm per pH unit, which is 4-fold higher than that of fluorescence-based sensing, while the sensitivity based on the variation of the lasing emission intensity is almost three orders of magnitude higher than that of fluorescence-based sensing. Our work presents a novel dual sensing paradigm in response to different pH conditions, which can greatly improve the reliability and discrimination of pH sensing.

CD34+ cell atlas of main organs implicates its impact on fibrosis.

RATIONALE: CD34+ cells are believed being progenitors that may be used to treat cardiovascular disease. However, the exact identity and the role of CD34+ cells in physiological and pathological conditions remain unclear. METHODS: We performed single-cell RNA sequencing analysis to provide a cell atlas of normal tissue/organ and pathological conditions. Furthermore, a genetic lineage tracing mouse model was used to investigate the role of CD34+ cells in angiogenesis and organ fibrosis. RESULTS: Single-cell RNA sequencing analysis revealed a heterogeneous population of CD34+ cells in both physiological and pathological conditions. Using a genetic lineage tracing mouse model, we showed that CD34+ cells not only acquired endothelial cell fate involved in angiogenesis, but also, CD34+ cells expressing Pi16 may transform into myofibroblast and thus participate in organ fibrosis. CONCLUSION: A heterogeneous CD34+ cells serve as a contributor not only to endothelial regeneration but also a wound healing response that may provide therapeutic insights into fibrosis.

Endothelial repair by stem and progenitor cells.

The integrity of the endothelial barrier is required to maintain vascular homeostasis and fluid balance between the circulatory system and surrounding tissues and to prevent the development of vascular disease. However, the origin of the newly developed endothelial cells is still controversial. Stem and progenitor cells have the potential to differentiate into endothelial cell lines and stimulate vascular regeneration in a paracrine/autocrine fashion. The one source of new endothelial cells was believed to come from the bone marrow, which was challenged by the recent findings. By administration of new techniques, including genetic cell lineage tracing and single cell RNA sequencing, more solid data were obtained that support the concept of stem/progenitor cells for regenerating damaged endothelium. Specifically, it was found that tissue resident endothelial progenitors located in the vessel wall were crucial for endothelial repair. In this review, we summarized the latest advances in stem and progenitor cell research in endothelial regeneration through findings from animal models and discussed clinical data to indicate the future direction of stem cell therapy.

Impact of Local Alloimmunity and Recipient Cells in Transplant Arteriosclerosis.

RATIONALE: Transplant arteriosclerosis is the major limitation to long-term survival of solid organ transplantation. Although both immune and nonimmune cells have been suggested to contribute to this process, the complex cellular heterogeneity within the grafts, and the underlying mechanisms regulating the disease progression remain largely uncharacterized. OBJECTIVE: We aimed to delineate the cellular heterogeneity within the allografts, and to explore possible mechanisms underlying this process. METHODS AND RESULTS: Here, we reported the transcriptional profiling of 11 868 cells in a mouse model of transplant arteriosclerosis by single-cell RNA sequencing. Unbiased clustering analyses identified 21 cell clusters at different stages of diseases, and focused analysis revealed several previously unknown subpopulations enriched in the allografts. Interestingly, we found evidence of the local formation of tertiary lymphoid tissues and suggested a possible local modulation of alloimmune responses within the grafts. Intercellular communication analyses uncovered a potential role of several ligands and receptors, including Ccl21a and Cxcr3, in regulating lymphatic endothelial cell-induced early chemotaxis and infiltration of immune cells. In vivo mouse experiments confirmed the therapeutic potential of CCL21 and CXCR3 neutralizing antibodies in transplant arteriosclerosis. Combinational use of genetic lineage tracing and single-cell techniques further indicate the infiltration of host-derived c-Kit+ stem cells as heterogeneous populations in the allografts. Finally, we compared the immune response between mouse allograft and atherosclerosis models in single-cell RNA-seq analysis. By analyzing susceptibility genes of disease traits, we also identified several cell clusters expressing genes associated with disease risk. CONCLUSIONS: Our study provides a transcriptional and cellular landscape of transplant arteriosclerosis, which could be fundamental to understanding the initiation and progression of this disease. CCL21/CXCR3 was also identified as important regulators of immune response and may serve as potential therapeutic targets in disease treatment.

Association of Inpatient Use of Angiotensin-Converting Enzyme Inhibitors and Angiotensin II Receptor Blockers With Mortality Among Patients With Hypertension Hospitalized With COVID-19.

RATIONALE: Use of ACEIs (angiotensin-converting enzyme inhibitors) and ARBs (angiotensin II receptor blockers) is a major concern for clinicians treating coronavirus disease 2019 (COVID-19) in patients with hypertension. OBJECTIVE: To determine the association between in-hospital use of ACEI/ARB and all-cause mortality in patients with hypertension and hospitalized due to COVID-19. METHODS AND RESULTS: This retrospective, multi-center study included 1128 adult patients with hypertension diagnosed with COVID-19, including 188 taking ACEI/ARB (ACEI/ARB group; median age 64 [interquartile range, 55-68] years; 53.2% men) and 940 without using ACEI/ARB (non-ACEI/ARB group; median age 64 [interquartile range 57-69]; 53.5% men), who were admitted to 9 hospitals in Hubei Province, China from December 31, 2019 to February 20, 2020. In mixed-effect Cox model treating site as a random effect, after adjusting for age, gender, comorbidities, and in-hospital medications, the detected risk for all-cause mortality was lower in the ACEI/ARB group versus the non-ACEI/ARB group (adjusted hazard ratio, 0.42 [95% CI, 0.19-0.92]; P=0.03). In a propensity score-matched analysis followed by adjusting imbalanced variables in mixed-effect Cox model, the results consistently demonstrated lower risk of COVID-19 mortality in patients who received ACEI/ARB versus those who did not receive ACEI/ARB (adjusted hazard ratio, 0.37 [95% CI, 0.15-0.89]; P=0.03). Further subgroup propensity score-matched analysis indicated that, compared with use of other antihypertensive drugs, ACEI/ARB was also associated with decreased mortality (adjusted hazard ratio, 0.30 [95% CI, 0.12-0.70]; P=0.01) in patients with COVID-19 and coexisting hypertension. CONCLUSIONS: Among hospitalized patients with COVID-19 and coexisting hypertension, inpatient use of ACEI/ARB was associated with lower risk of all-cause mortality compared with ACEI/ARB nonusers. While study interpretation needs to consider the potential for residual confounders, it is unlikely that in-hospital use of ACEI/ARB was associated with an increased mortality risk.

Stem/Progenitor Cells and Pulmonary Arterial Hypertension.

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by endothelial dysfunction and vascular remodeling. Despite significant advancement in our understanding of the pathogenesis of PAH in recent years, treatment options for PAH are limited and their prognosis remains poor. PAH is now seen as a severe pulmonary arterial vasculopathy with structural changes driven by excessive vascular proliferation and inflammation. Perturbations of a number of cellular and molecular mechanisms have been described, including pathways involving growth factors, cytokines, metabolic signaling, elastases, and proteases, underscoring the complexity of the disease pathogenesis. Interestingly, emerging evidence suggests that stem/progenitor cells may have an impact on disease development and therapy. In preclinical studies, stem/progenitor cells displayed an ability to promote endothelial repair of dysfunctional arteries and induce neovascularization. The stem cell-based therapy for PAH are now under active investigation. This review article will briefly summarize the updates in the research field, with a special focus on the contribution of stem/progenitor cells to lesion formation via influencing vascular cell functions and highlight the potential clinical application of stem/progenitor cell therapy to PAH.

Cardiomyocyte peroxisome proliferator-activated receptor α is essential for energy metabolism and extracellular matrix homeostasis during pressure overload-induced cardiac remodeling.

Peroxisome proliferator-activated receptor α (PPARα), a ligand-activated nuclear receptor critical for systemic lipid homeostasis, has been shown closely related to cardiac remodeling. However, the roles of cardiomyocyte PPARα in pressure overload-induced cardiac remodeling remains unclear because of lacking a cardiomyocyte-specific Ppara-deficient (PparaΔCM) mouse model. This study aimed to determine the specific role of cardiomyocyte PPARα in transverse aortic constriction (TAC)-induced cardiac remodeling using an inducible PparaΔCM mouse model. PparaΔCM and Pparafl/fl mice were randomly subjected to sham or TAC for 2 weeks. Cardiomyocyte PPARα deficiency accelerated TAC-induced cardiac hypertrophy and fibrosis. Transcriptome analysis showed that genes related to fatty acid metabolism were dramatically downregulated, but genes critical for glycolysis were markedly upregulated in PparaΔCM hearts. Moreover, the hypertrophy-related genes, including genes involved in extracellular matrix (ECM) remodeling, cell adhesion, and cell migration, were upregulated in hypertrophic PparaΔCM hearts. Western blot analyses demonstrated an increased HIF1α protein level in hypertrophic PparaΔCM hearts. PET/CT analyses showed an enhanced glucose uptake in hypertrophic PparaΔCM hearts. Bioenergetic analyses further revealed that both basal and maximal oxygen consumption rates and ATP production were significantly increased in hypertrophic Pparafl/fl hearts; however, these increases were markedly blunted in PparaΔCM hearts. In contrast, hypertrophic PparaΔCM hearts exhibited enhanced extracellular acidification rate (ECAR) capacity, as reflected by increased basal ECAR and glycolysis but decreased glycolytic reserve. These results suggest that cardiomyocyte PPARα is crucial for the homeostasis of both energy metabolism and ECM during TAC-induced cardiac remodeling, thus providing new insights into potential therapeutics of cardiac remodeling-related diseases.